Herbicide compositions of extended soil life

ABSTRACT

Herbicidally active thiolcarbamates are employed in combination with certain organophosphorous compounds having the formula ##STR1## in which R 4  is selected from the group consisting of C 1  -C 4  alkyl, C 1  -C 4  alkoxy and C 1  -C 4  alkylthio; R 5  is selected from the group consisting of C 1  -C 4  alkoxy and C 1  -C 4  alkylthio; R 6  is selected from the group consisting of C 2  -C 6  alkylene and C 2  -C 6  alkenylene; R 7  is selected from the group consisting of hydrogen, phenyl, C 1  -C 4  alkyl and C 2  -C 4  alkenyl, all optionally substituted with up to two halogens; X is oxygen or sulfur; and n is zero or one. As a result, the herbicidal effectiveness of the thiocarbamate is enhanced and prolonged, rendering a single application of the herbicide effective over a longer period of time.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of Application Ser. No.495,285, filed May 16, 1983, now abandoned which is a continuation ofapplication Ser. No. 350,793, filed Feb. 22, 1982, now abandoned; whichin turn is a continuation of application Ser. No. 163,675, filed June27, 1980, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to herbicidal compositions and methods of use. Inparticular, this invention relates to herbicidal compositions comprisingan herbicidally active thiocarbamate in combination with certainorganophosphorus compounds, the latter serving to prolong theeffectiveness of a single application of the thiocarbamate incontrolling undesired plant growth.

Thiocarbamates are well known in the argicultural art as herbicidesuseful for weed control in crops such as corn, potatoes, beans, beets,spinach, tobacco, tomatoes, alfalfa, rice and others. Thiocarbamates areprimarily used in pre-emergence application, and are particularlyeffective when incorporated into the soil prior to the planting of thecrop. The concentration of the thiocarbamate in the soil is greatestimmediately after application of the compound. How long thereafter theinitial concentration is retained depends in large part on theparticular soil used. The rate at which the thiocarbamate concentrationdeclines following its application varies from one type of soil to thenext. This is evident both in the observable extent of weed control andin the detectable presence of undegraded thiocarbamate remaining in thesoil after considerable time has elapsed.

It is therefore an object of this invention to increase the soilpersistence of thiocarbamate herbicides and thus improve theirherbicidal effectiveness.

BRIEF DESCRIPTION OF THE INVENTION

It has now been discovered that the soil persistence of certainherbicidally active thiocarbamates is significantly extended by thefurther addition to the soil of certain extender compounds in the formof organophosphorus compounds, which have little or no herbicidalactivity of their own and do not decrease the herbicidal activity of thethiocarbamate. This improvement in the soil presistence of thiocarbamatemanifests itself in a variety of ways. It can be shown, for example, bysoil analyses taken at regular intervals, that the rate of decrease ofthe thiocarbamate content of the soil is substantially lessened.Improved soil persistence can also be shown by improvements inherbicidal efficacy, as evidenced by a higher degree of weed injurybrought about when the extender compound increases the soil persistenceof the thiocarbamate, prolonging its effective life.

Examples 1 and 2 below illustrate two different methods of proving theextending activity of the organophosphorus compounds of the instantinvention. Example 1 provides chemical assay data whereas Example 2provides bioassay data. The soil in both examples is pre-treated with athiocarbamate herbicide to simulate field conditions wherein a field hasbeen repeatedly treated with a thiocarbamate herbicide. However, insteadof a year inbetween treatments as in the case of seasonally cultivatedfields, the soil in the experiments herein was retreated with theherbicide within weeks of the first treatment. Such a short retreatmentperiod provides a soil which is conditioned to degrade thiocarbamatesrapidly for experimental purposes.

The chemical assay data of Example 1 shows by chromatographic analysisthat the thiocarbamate herbicide's soil life is extended over time byevidencing that the parts per million of the herbicide is much greaterwhen an organophosphorus extender is present than when it is absent.

The bioassay data of Example 2 shows the soil life extension ofthiocarbamate herbicides by the extension of their herbicidal activityin soil also conditioned for rapid degradation of thiocarbamateherbicides.

In particular, this invention relates to a novel herbicidal compositioncomprising

(a) an herbicidally effective amount of a thiocarbamate having theformula ##STR2## in which R¹, R², and R³ are independently C₂ -C₄ alkyl;and

(b) an amount of an organophosphorus compound sufficient to extend thesoil life of said thiocarbamate, and organophosphorus compound havingthe formula ##STR3## in which R⁴ is selected from the group consistingof C₁ -C₄ alkyl, C₁ -C₄ alkoxy and C₁ -C₄ alkylthio,

R⁵ is selected from the group consisting of C₁ -C₄ alkoxy and C₁ -C₄alkylthio,

R⁶ is selected from the group consisting of C₂ -C₆ alkylene and C₂ -C₆alkenylene,

R⁷ is selected from the group consisting of hydrogen, phenyl, C₁ -C₄alkyl, and C₂ -C₄ alkenyl, all optionally substituted with up to twohalogens,

X is oxygen or sulfur, and

n is zero or one.

Within the scope of the present invention, certain embodiments arepreferred, namely:

In the thiocarbamate formula, R¹ is preferably ethyl, and R² and R³ areeach preferably independently n-propyl or isopropyl.

In preferred organophosphorus compounds:

R⁴ is selected from the group consisting of C₁ -C₄ alkyl, C₁ -C₄ alkoxy,and C₁ -C₄ alkylthio,

R⁵ is selected from the group consisting of C₁ -C₄ alkoxy and C₁ -C₄alkylthio,

R⁶ is selected from the group consisting of C₂ -C₄ alkylene and C₂ -C₄alkenylene,

R⁷ is selected from the group consisting of hydrogen, phenyl, and C₁ -C₃alkyl,

X is oxygen or sulfur, and

n is zero or one.

This invention further relates to a method of controlling undesirablevegetation comprising applying the above composition to the locus wherecontrol is desired.

The terms "alkyl," "alkoxy," "alkylthio," and "alkenyl" are intended toinclude both straight-chain and branched-chain groups, such as methyl,ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, methoxy,ethoxy, isopropoxy, tert-butoxy, methylthio, ethylthio, n-butylthio,allyl, 2-methylallyl, etc. The terms "alkylene" and "alkenylene" areused herein to denote a bivalent hydrocarbon radical which are saturatedor unsaturated, respectively, and are also intended to include bothstraight-chain and branched-chain groups. Examples are --CH₂ CH₂ CH₂ --,--CH₂ CH(CH₃)CH₂ --, --CH(CH₃)CH₂ --, --C(CH₃)₂ CH₂ --, --CH₂ C(CH₃)₂CH₂ --, --CH₂ CH(C₂ H₅)CH₂ --, --CH═CH--, --C(CH₃)═CH--, etc. All carbonatoms ranges in this specification and the appended claims are intendedto be inclusive of their upper and lower limits.

The term "herbicide", as used herein, means a compound or compositionwhich controls or modifies the growth of plants. By the term"herbicidally effective amount" is meant any amount of such compound orcomposition which causes a modifying effect upon the growth of plants.By "plants" is meant germinant seeds, emerging seedlings and establishedvegetation, including roots and above-ground portions. Such controllingor modifying effects include all deviations from natural development,such as killing, retardation, defoliation, desiccation, regulation,stunting, tillering, stimulation, leaf burn, dwarfing and the like.

The phrase "to extend the soil life of said thiocarbamate" as usedherein means to retard the rate at which molecules of thiocarbamate arebroken down into decomposition products when in contact with soil and/orprolong the period of time following application in which herbicidaleffects can be observed. This applies both to field sites where repeatedapplications of thiocarbamates have resulted in decreasing herbicidaleffectiveness, and to field sites where a decline in activity isdetected over time regardless of the prior history of herbicidalapplications. An extended soil life can be manifest in a slower rate ofdecline of weed-killing activity, or an increased half-life ofthiocarbamate concentration in the soil. Other techniques of determiningsoil life are readily apparent to one skilled in the art.

DETAILED DESCRIPTION OF THE INVENTION

The thiocarbamates within the scope of the present invention can beprepared by the process described in U.S. Pat. No. 2,913,327 (Tilles etal., Nov. 17, 1959). The organophosphorus compounds can be prepared bythe process described in U.S. Pat. Nos. 3,714,716 (Gaughan, Jan. 30,1973) and 3,694,451 (Mihailovski, Sept. 26, 1972).

The objects of the present invention are achieved by applying theorganophosphorus extender compound to the soil at an agricultural fieldsite in conjunction with the thiocarbamate herbicide. The two compoundscan be applied simultaneously in a single mixture or in separateformulations, or they can be applied in succession, with either onefollowing the other. In successive application, it is preferable to addthe compounds as close in time as possible.

The herbicide extending effect is operable over a wide range of ratiosof the two compounds. It is most convenient, however, to apply thecompounds at a ratio of about 1:1 to about 20:1 (herbicide/extender) ona weight basis, preferably about 1:1 to about 10:1, and most preferablyabout 1:1 to about 5:1.

Thiocarbamate herbicides useful in the present invention include S-ethyldi-n-propylthiocarbamate, S-ethyl diisobutylthiocarbamate, S-n-propyldi-n-propylthiocarbamate, and S-n-propyl ethyl-n-butylthiocarbamate.

The variety of crops on which the present composition is useful can besignificantly broadened by the use of an antidote to protect the cropfrom injury and render the composition more selective against weeds.

For antidote descriptions and methods of use, reference is made to U.S.Pat. No. 3,959,304, issued to E. G. Teach on May 25, 1976; U.S. Pat. No.3,989,503, issued to F. M. Pallos et al. on Nov. 2, 1976; U.S. Pat. No.4,021,224, issued to F. M. Pallos et al. on May 3, 1977; U.S. Pat. No.3,131,509 issued to O. L. Hoffman on May 5, 1964; and U.S. Pat. No.3,564,768, issued to O. L. Hoffman on Feb. 3, 1971.

Examples of useful antidotes include acetamides such asN,N-diallyl-2,2-dichloroacetamide and N,N-diallyl-2-chloroacetamide,oxazolidines such as 2,2,5-trimethyl-N-dichloroacetyl oxazolidine and2,2-spirocyclohexyl-N-dichloroacetyl oxazolidine, and 1,8-naphthalicanhydride. For maximum effect, the antidote is present in thecomposition in a non-phytotoxic, antidotally effective amount. By"non-phytotoxic" is meant an amount which causes at most minor injury tothe crop. By "antidotally effective" is meant an amount whichsubstantially decreases the extent of injury caused by the herbicide tothe crop. The preferred weight ratio of herbicide to antidote is about0.1:1 to about 30:1. The most preferred range for this ratio is about3:1 to about 20:1.

The following examples are offered to illustrate the utility of thepresent invention, and are intended neither to limit nor define theinvention in any manner.

EXAMPLE 1

These examples show, by soil analysis, the effectiveness of thecompounds of the present invention in extending the soil life of thethiocarbamate herbicides. The herbicide used in these tests was S-ethyldi-n-propylthiocarbamate, commonly known as EPTC. The soil was a sandyloam soil obtained from Sunol, Calif., containing approximately (on aweight basis) 64% sand, 29% silt, and 7% clay, determined by mechanicalmeans. The total organic content of the soil was approximately 4% byweight and the pH was 6.8, both determined by chemical analysis.

The test procedure involved an initial pre-treatment of the soil tosimulate field conditions where the soil had been previously treatedwith EPTC, followed by a soil persistence test, as described below.

A. Soil Pre-Treatment

An emulsion was prepared by diluting an emulsifiable liquid concentratecontaining 6 lb/gal (0.72 kg/l) of the thiocarbamate in 100 ml of water,such that the concentration of thiocarbamate in the resulting emulsionwas 4000 mg/l. Five ml of this emulsion was then added to 10 lb (4.54kg) of soil and the mixture was mixed in a rotary mixer for 10-20seconds.

Round plastic containers, 9 inches (22.9 cm) in diameter by 9 inches(22.9 cm) deep, were then filled with the sandy loam soil, which wastamped and leveled with a row marker to impress three rows across thewidth of each container. Two rows were seeded with DeKalb XL-45A cornZea mays (L.), and one row was seeded with barnyardgrass Echinochloacrusgalli (L.). Sufficient seeds were planted to produce severalseedlings per row. The containers were then placed in a greenhousemaintained at 20° C. to 30° C. and watered daily by sprinkler.

Five weeks after treatment, the soil was allowed to dry out and theplant foliage was removed. The soil was then passed through a 0.25 inch(0.64 cm) screen, followed by a 2 millimeter (mm) screen, to removeplant roots and clods.

B. Soil Persistence Test

A 100-gram quantity (air-dry basis) of the pre-treated soil was placedin an 8-ounce (0.25 liter) wide-mouth glass bottle. The sameemulsifiable concentrate described in Part A above was appropriatelydiluted in water such that a 5-ml portion added to the soil wouldproduce a herbicide concentration of 6 ppm (weight) in the soil. This isequivalent to an application rate of 6 pounds per acre (6.7 kilogramsper hectare) in a field where the herbicide is incorporated into thesoil through a depth of about 2 inches (5.08 cm) soon after application.A selected extender compound in technical (nonformulated) form was thendiluted in an acetone-water mixture such that a one-ml portion added tothe soil would produce a concentration of 4 ppm by weight, equivalent to4 pounds per acre (4.5 kilograms per hectare). On these bases, theherbicide and extender were added to the bottle containing the soil. Thebottle was then sealed with a lid and shaken manually for approximately15 minutes.

Following such treatment, the soil was moistened with 20 ml deionizedwater. The bottle was then covered with a watch glass to maintainaerobic conditions and to prevent rapid soil drying, and placed in acontrolled environmental chamber in darkness, where the temperature wasmaintained constant at 25° C.

Two days later, the bottle was removed from the environmental chamberand 50 ml of water and 100 ml of toluene were added. The bottle was thentightly sealed with a lid containing a cellophane liner, and vigorouslyshaken on a variable speed, reciprocating shaker (Eberbach Corp. Model6000) set at approximately 200 excursions per minute for one hour. Aftershaking, the bottle contents were allowed to settle, and a 10 ml aliguotof toluene was transferred by pipette into a glass vial and sealed witha polyseal cap. The toluene extract was analyzed for herbicidal contentby gas chromatography. The chromatogram data was then converted toequivalent soil concentrations in parts per million (ppm) by weight ofthe herbicide.

The results are shown in Table 1 below, where a variety of compoundswere tested in two separately treated batches of soil. A control runwithout an extender compound was conducted for each soil batch, to showhow the drop in herbicide concentration was affected by the extendercompound. In each case, the quantity of herbicide remaining in the soilafter two days was dramatically increased when the extender compound wasadded.

                                      TABLE 1                                     __________________________________________________________________________    2-DAY SOIL PERSISTENCE DATA                                                   Herbicide:                                                                          SEthyl di-n-propylthiolcarbamate (EPTC) at 6 lb/A                             (6 ppm in soil)                                                         Extender:                                                                           As shown at 4 lb/A (4 ppm in soil)                                                                   EPTC Residue                                     Extender                     After 2 Days (ppm)                               Compound                     With  Without                                    No.     Structural Formula   Extender                                                                            Extender                                   __________________________________________________________________________    Soil Batch A:                                                                          ##STR4##            3.15  1.32                                       2                                                                                      ##STR5##            1.71  1.32                                       3                                                                                      ##STR6##            0.97  1.32                                       4                                                                                      ##STR7##            2.65  1.32                                       5                                                                                      ##STR8##            3.07  1.32                                       6                                                                                      ##STR9##            2.28  1.32                                       7                                                                                      ##STR10##           2.18  1.32                                       8                                                                                      ##STR11##           2.12  1.32                                       9                                                                                      ##STR12##           2.38  1.32                                       10                                                                                     ##STR13##           3.16  1.32                                       Soil Batch B:                                                                 11                                                                                     ##STR14##           3.34  0.22                                       __________________________________________________________________________

EXAMPLE 2 TEST PROCEDURES

This example offers herbicidal activity test data for manyrepresentative extender compounds within the scope of this inventionshowing their effectiveness in improving the herbicidal activity ofthiocarbamates. The effect is observed by comparing the extent of weedcontrol in test flats treated with a thiocarbamate against thatoccurring in similar flats treated with both the thiocarbamate and theextender. The soil used in these tests was a sandy loam soil from Sunol,Calif., which was pre-treated with the herbicide to simulate a typicalfield which had received previous herbicide applications.

The extender compounds tested according to the following procedure areas follows:

                                      TABLE OF COMPOUNDS                          __________________________________________________________________________     ##STR15##                                                                    Extender                                                                      Cmpd. No.                                                                            R.sup.4                                                                             R.sup.5                                                                             R.sup.6  R.sup.7   X                                       __________________________________________________________________________    1      CH.sub.3 O                                                                          CH.sub.3 O                                                                          C.sub.2 H.sub.4                                                                         ##STR16##                                                                              O                                       3      C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5 O                                                                    ##STR17##                                                                             CH.sub.2 CH(CH.sub.3).sub.2                                                             O                                       4      CH.sub.3 O                                                                          CH.sub.3 O                                                                          C.sub.2 H.sub.4                                                                        CH.sub.2 CHCH.sub.2                                                                     S                                       5      C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5 O                                                                    ##STR18##                                                                             C.sub.2 H.sub.5                                                                         O                                       6      CH.sub.3 O                                                                          CH.sub.3 O                                                                          C.sub.2 H.sub.5                                                                        CH.sub.2 CHCCl.sub. 2                                                                   S                                       7      C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5 O                                                                   CHCH     CH.sub.3  S                                       8      C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5 O                                                                   C.sub.2 H.sub.4                                                                        CH.sub.3  S                                       11     C.sub.2 H.sub.5                                                                     CH.sub.3 S                                                                          CHCH     CH.sub.3  S                                       12     CH.sub.3 O                                                                          CH.sub.3 O                                                                           ##STR19##                                                                              ##STR20##                                                                              O                                       __________________________________________________________________________

A. Soil Pre-Treatment

The soil was pre-treated in each instance at 3 lb/A. Where thethiocarbamate tested was S-ethyl diisobutylthiocarbamate, a 6.7 lb/gal(85.2%) emulsifiable liquid concentrate in a 24:1 ratio with theantidote N,N-diallyl-2,2-dichloroacetamide was employed. Where thethiocarbamate was S-propyl N,N-dipropylthiocarbamate, the soil waspretreated with either an emulsifiable liquid concentrate in a 12:1ratio with the antidote N,N-diallyl-2,2-dichloroacetamide or anemulsifiable liquid concentrate of the herbicide alone. In eachinstance, the emulsifiable liquid concentrates were diluted in 200 ml ofwater, such that the resulting concentration of herbicide in thesolution was 2000 mg/l. Two hundred ml of this solution was then addedto 200 lb (90.8 kg) of soil to which 17--17--17 fertilizer (N--P₂ O₅--K₂ O on a weight basis) has been previously added to a concentrationof 50 ppm by weight with respect to the soil. The mixture was mixed in arotary mixer for 10 to 30 minutes.

The soil was then placed in round plastic containers, 7.5 inches (19.0cm) in diameter by 7.5 inches (19.0 cm) deep. The soil was tamped andleveled with a row marker to impress one row across the width of eachcontainer. This row was seeded with watergrass (Echinochloa crusgalli).Sufficient seeds were planted to produce several seedlings. Thecontainers were then placed in a greenhouse maintained at 20° C. to 30°C. and watered daily by sprinkler.

Five weeks after treatment, the soil was allowed to dry out and theplant foliage was removed. The soil was then passed through a 0.25 inch(0.64 cm) screen to remove plant roots and clods. The soil was thentreated according to the procedures (B) below. Where the pre-treatmentwas with S-propyl N,N-dipropyl thiocarbamate alone the soil was notemployed for one or more months, whereas the thiocarbamate plus antidoteconditioned soil was then used shortly as follows in (B).

B. Herbicide Test

Solutions were prepared by diluting those emulsifiable liquidconcentrates described above as containing the antidoteN,N-diallyl-2,2-dichloroacetamide and thiocarbamate in 650 ml of watersuch that the resulting concentration of herbicide in the solution was1.48 mg/ml. Five ml of this solution when added to three pounds of soilyielded a quantity in the soil equivalent to three pounds per acre.

The extender compounds were used in technical form. These materials wereadded to 5 ml acetate and 21 ml water such that the resultingconcentration of the extender in the solution was 1.54 mg/ml. Theacetone contained 1% of an emulsifier/surfactant. Five ml of thissolution when added to three pounds of soil yielded a quantity in thesoil equivalent to four pounds per acre.

Five ml of the extender solution and 5 ml of the herbicide solution weretank-mixed. The resultant mixture of 10 ml was then added to 3 lbs ofsoil and incorporated into the soil by a rotary mixer. Thus, 10 ml ofthe mixture and 3 pounds of soil were placed in rotary mixter andincorporated.

The treated soil was then placed in aluminum flats which wereapproximately 2.5 inches deep, 3.5 inches wide, and 7.5 inches long. Thesoil was tamped and leveled with a row marker to impress six rows acrossthe width of the flat. The test weeds were as follows:

    ______________________________________                                        COMMON                                                                        NAME    ABBREVIATION   SCIENTIFIC NAME                                        ______________________________________                                        watergrass                                                                            WG             Echinochloa crusgalli (L.)                             wild oats                                                                             WO             Avena fatua (L.)                                       wild cane                                                                             WC             Sorghum bicolor (L.) Moench                            ______________________________________                                    

R-10 milo (Sorghum bicolor) was also used as a plant growth indicator.Two rows of watergrass were planted. One row of each of the other weedsand plant growth indicator were planted.

Sufficient seeds were planted to produce several seedlings per inch ineach row. The flats were then placed in a greenhouse maintained at 70°to 85° F. (21° to 30° C.) and watered daily by sprinkler.

Sixteen days after treatment, the degree of weed control and corn injurywere estimated and recorded as a percentage compared to the growth ofthe same species in a check flat of the same age which had been seededin conditioned soil but not treated with either an herbicide or anextender. The rating scale ranges from 0 to 100%, where 0 equals noeffect with plant growth equal to the untreated check, and 100 equalscomplete kill.

An asterisk in Table 2 indicates that the treatment was run in soilpre-treated with the thiocarbamate S-propyl N,N-dipropyl thiocarbamate,alone, that is, without an antidote. The results are listed in Table 2.

The average percentage of weed control is the average for theabove-identified weed species and plant growth indicator. Controlexperiments (herbicide alone with an extender present) were included ineach batch for comparison. Substantial improvements in average percentweed control over the control experiments are evident. The herbicidalefficacy of the thiocarbamate three weeks after application was muchimproved by the use of the extender.

                  TABLE 2                                                         ______________________________________                                        HERBICIDAL ACTIVITY TESTS                                                     Treatment         Average % Control                                           Herbicide    Extender of 4 Grass Species                                      ______________________________________                                        A            --       19                                                      (average of                                                                   3 trials)                                                                     A            1        45                                                      A            3        61                                                      A            4        61                                                      A            5        60                                                      A            6        45                                                      A            11       48                                                      A            12       42                                                      A            --        15*                                                    (average of                                                                   3 trials)                                                                     A            7         58*                                                    A            8         67*                                                    B            --        6                                                      (average of                                                                   3 trials)                                                                     B            1         9                                                      B            3        92                                                      B            4        29                                                      B            5        27                                                      B            6        65                                                      B            7        --                                                      B            8        --                                                      B            11       33                                                      B            12       27                                                      ______________________________________                                         Herbicide A: S--propyl N,N--dipropyl thiocarbamate in a 12:1 weight ratio     with the antidote N,N--diallyl2,2-dichloroacetamide                           Herbicide B: S--ethyl N,N--diisobutyl thiocarbamate in a 24:1 weight rati     with the antidote N,N--diallyl2,2-dichloroacetamide                           Extender: Indicated by Compound No. (see Table I)                             Herbicide Application Rate: 3 lb/Acre                                         Extender Application Rate: 4 lb/Acre                                     

TEST PROCEDURES WITHOUT ANTIDOTE

The same procedures were followed as stated above under procedure withantidote supra except that no antidote is present in the emulsifiableliquid concentrates with the thiocarbamates--S-ethyl N,N-diisobutylthiocarbamate (77.3% active ingredient) and S-propyl N,N-dipropylthiocarbamate (89% active ingredient); and except that the rating wastaken twenty-two days after treatment.

                  TABLE 3                                                         ______________________________________                                        HERBICIDAL ACTIVITY TESTS                                                     Treatment    Extender      Average % Control                                  Herbicide                                                                             Extender Application Rate                                                                            of 4 Grass Species                             ______________________________________                                        A       --       --            18                                             average of                                                                    3 trials)                                                                     A       3        2             62                                             A       3        4             76                                             B       --       --            31                                             (average of                                                                   3 trials)                                                                     B       3        2             49                                             B       3        4             63                                             ______________________________________                                         Herbicide A: S--propyl N,N--dipropyl thiocarbamate                            Herbicide B: S--ethyl N,N--diisobutyl thiocarbamate                           Extender: Indicated by Compound No. 3 (see Table I)                           Herbicide Application Rate: 3 lb/Acre                                         Extender Application Rate: 2 and 4 lb/Acre, as indicated                 

METHODS OF APPLICATION

The herbicidal compositions of the present invention are useful incontrolling the growth of undesirable vegetation by pre-emergence orpost-emergence application to the locus where control is desired,including pre-plant and post-plant soil incorporation as well as surfaceapplication. The compositions are generally embodied in formulationssuitable for convenient application. Typical formulations containadditional ingredients or diluent carriers which are either inert oractive. Examples of such ingredients or carriers are water, organicsolvents, dust carriers, granular carriers, surface active agents, oiland water, water-oil emulsions, wetting agents, dispersing agents, andemulsifying agents. The herbicidal formulations generally take the formof dusts, emulsifiable concentrates, granules and pellets, ormicrocapsules.

A. DUSTS

Dusts are dense powder compositions which are intended for applicationin dry form. Dusts are characterized by their free-flowing and rapidsettling properties so that they are not readily windborne to areaswhere their presence is not desired. They obtain primarily an activematerial and a dense, free-flowing, solid carrier.

Their performance is sometimes aided by the inclusion of a wettingagent, and convenience in manufacture frequently demands the inclusionof an inert, absorptive grinding aid. For the dust compositions of thisinvention, the inert carrier may be either of vegetable or mineralorigin, the wetting agent is preferably anionic or nonionic, andsuitable absorptive grinding aids are of mineral origin.

Suitable classes of inert solid carriers for use in the dustcompositions are those organic or inorganic powders which possess highbulk density and are very free-flowing. They are also characterized bylow surface area and poor liquid absorptivity. Suitable grinding aidsare natural clays, diatomaceous earths, and synthetic mineral fillersderived friom silica or silicate. Among ionic and nonionic wettingagents, the most suitable are the members of the group known to the artas wetting agents and emulsifiers. Although solid agents are preferredbecause of ease of incorporation, some liquid nonionic agents are alsosuitable in the dust formulations.

Preferred dust carriers are micaceous talcs, pyrophyllite, dense kaolinclays, tobacco dust and ground calcium phosphate rock. Preferredgrinding aids are attapulgite clay, diatomaceous silica, synthetic finesilica and synthetic calcium and magnesium silicates.

Most preferred wetting agents are alkylbenzene and alkyl-naphthalenesulfonates, sulfated fatty alcohols, amines or acid amides, long chainacid esters of sodium isothionate, esters of sodium sulfosuccinate,sulfated or sulfonated fatty acid esters, petroleum sulfonates,sulfonated vegetable oils, and ditertiary acetylenic glycols. Preferreddispersants are methyl cellulose, polyvinyl alcohol, lignin sulfonates,polymeric alkylnaphthalene sulfonates, sodium naphthalenesulfonate,polymethylene bisnaphthalenesulfonate, and sodium-N-methyl-N-(long chainacid) taurates.

The inert solid carriers in the dusts of this invention are usuallypresent in concentrations of from about 30 to 90 weight percent of thetotal composition. The grinding aid will usually constitute 5 to 50weight percent of the compositions, and the wetting agent willconstitute from about 0 to 1.0 weight percent of the composition. Dustcompositions can also contain other surfactants such as dispersingagents in concentrations of up to about 0.5 weight percent, and minoramounts of anticaking and antistatic agents. The particle size of thecarrier is usually in the range of 30 to 50 microns.

B. EMULSIFIABLE CONCENTRATES

Emulsifiable concentrates are usually solutions of the active materialsin nonwater-miscible solvents together with an emulsifying agent. Priorto use, the concentrate is diluted with water to form a suspendedemulsion of solvent droplets.

Typical solvents for use in emulsifiable concentrates include weed oils,chlorinated hydrocarbons, and nonwater-miscible ethers, esters, andketones.

Typical emulsifying agents are anionic or nonionic surfactants, ormixtures of the two. Examples include long-chain alkyl or mercaptanpolyethoxy alcohols, alkylaryl polyethoxy alcohols, sorbitan fatty acidesters, polyoxyethylene ethers with sorbitan fatty acid esters,polyoxyethylene glycol esters with fatty or rosin acids, fatty alkylolamide condensates, calcium and amine salts of fatty alcohol sulfates,oil soluble petroleum sulfonates, or preferably mixtures of theseemulsifying agents. Such emulsifying agents will comprise from about 1to 10 weight percent of the total composition.

Thus, emulsifiable concentrates of the present invention will consist offrom about 15 to about 50 weight percent active material, about 40 to 82weight percent solvent, and about 1 to 10 weight percent emulsifier.Other additives such as spreading agents and stickers can also beincluded.

C. GRANULES AND PELLETS

Granules and pellets are physically stable, particulate compositionscontaining the active ingredients adhering to or distributed through abasic matrix of a coherent, inert carrier with macroscopic dimensions. Atypical particle is about 1 to 2 millimeters in diameter. Surfactantsare often present to aid in leaching of the active ingredients from thegranule or pellet.

The carrier is preferably of mineral origin, and generally falls withinone of two types. The first are porous, absorptive, preformed granules,such as preformed and screened granular attapulgite or heat expanded,granular, screened vermiculite. On either of these, a solution of theactive agent can be sprayed and will be absorbed at concentrations up to25 weight percent of the total weight. The second, which are alsosuitable for pellets, are initially powdered kaolin clays, hydratedattapulgite, or bentonite clays in the form of sodium, calcium, ormagnesium bentonites. Water-soluble salts, such as sodium salts, mayalso be present to aid in the disintegration of granules or pellets inthe presence of moisture. These ingredients are blended with the activecomponents to give mixtures that are granulated or pelleted, followed bydrying, to yield formulations with the active component distributeduniformly throughout the mass. Such granules and pellets can also bemade with 25 to 30 weight percent active component, but more frequentlya concentration of about 10 weight percent is desired for optimumdistribution. The granular compositions of this invention are mostuseful in a size range of 15-30 mesh.

The surfactant is generally a common wetting agent of anionic ornonionic character. The most suitable wetting agents depend upon thetype of granule used. When preformed granules are sprayed with activematerial in liquid form the most suitable wetting agents are nonionic,liquid wetters miscible with the solvent. These are compounds mostgenerally known in the art as emulsifiers, and comprise alkylarylpolyether alcohols, alkyl polyether alcohols, polyoxyethylene sorbitanfatty acid esters, polyethylene glycol esters with fatty or rosin acids,fatty alkylol amide condensates, oil solution petroleum or vegetable oilsulfonates, or mixtures of these. Such agents will usually comprise upto about 5 weight percent of the total composition.

When the active ingredient is first mixed with a powdered carrier andsubsequently granulated, or pelleted, liquid nonionic wetters can stillbe used, but it is usually preferable to incorporate at the mixing stageone of the solid, powdered anionic wetting agents such as thosepreviously listed for the wettable powders. Such agents will comprisefrom about 0 to 2 weight percent of the total composition.

Thus, the preferred granular or pelleted formulations of this inventioncomprise about 5 to 30 percent by weight active material, about 0 to 5weight percent wetting agent, and about 65 to 95 weight percent inertmaterial carrier, as these terms are used herein.

D. MICROCAPSULES

Microcapsules consist of fully enclosed droplets or granules containingthe active materials, in which the enclosing material is an inert porousmembrane, arranged to allow escape of the enclosed materials to thesurrounding medium at controlled rates over a specified period.

Encapsulated droplets are typically about 1 to 50 microns in diameter.The enclosed liquid typical constitutes about 50 to 95% of the weight ofthe entire capsule, and may contain a small amount of solvent inaddition to the active materials.

Encapsulated granules are characterized by porous membranes sealing theopenings of the granule carrier pores, trapping the liquid containingthe active components inside for controlled release. A typical granulesize ranges from 1 millimeter to 1 centimeter in diameter. Inagricultural usage, the granule size is generally about 1 to 2millimeters in diameter. Granules formed by extrusion, agglomeration, orprilling are useful in the present invention as well as materials intheir naturally occurring form. Examples of such carriers arevermiculite, sintered clay granules, kaolin, attapulgite clay, sawdust,and granular carbon.

Useful encapsulating materials include natural and synthetic rubbers,cellulosic materials, styrene-butadiene copolymers, polyacrylonitriles,polyacrylates, polyesters, polyamides, polyurethanes, and starchxanthates.

E. IN GENERAL

Each of the above formulations can be prepared as a package containingboth the herbicide and the extender together with the other ingredientsof the formulation (diluents, emulsifiers, surfactants, etc.). Theformulations can also be prepared by a tank mix method, in which theingredients are obtained separately and combined at the grower site. Theherbicide and extender may both be used in the same type of formulationor a different formulation may be used for each, e.g. the herbicide maybe in microcapsule form while the extender may be an emulsifiableconcentrate, or vice versa.

As a further alternative, the herbicide and extender can be appliedsequentially, with either being applied first. This is a less preferredmethod, however, since more effective results are obtained withsimultaneous application.

In general, any conventional method of application can be used. Thelocus of application can be soil, seeds, seedlings, or the actualplants, as well as flooded fields. Soil application is preferred. Dustsand liquid compositions can be applied by the use of powder dusts, boomand hand sprayers, and spray dusters. The compositions can also beapplied from airplanes as dusts and sprays because they are effective invery low dosages. In order to modify or control the growth ofgerminating seeds or emerging seedlings, as a typical example, the dustand liquid compositions are applied to the soil according toconventional methods and are distributed in the soil to a depth of atleast one-half inch below the soil surface. It is not necessary that thephytotoxic compositions be admixed with the soil particles. Instead,these compositions can be applied merely by spraying or sprinkling thesurface of the soil. The phytotoxic compositions of this invention canalso be applied by addition to irrigation water supplied to the field tobe treated. This method of application permits the penetration of thecompositions into the soil as the water is absorbed therein. Dustcompositions, granular compositions or liquid formulations applied tothe surface of the soil can be distributed below the surface of the soilby conventional means such as discing, dragging or mixing operations.

The herbicide/extender compositions can also be applied to the soilthrough irrigation systems. According to this technique, thecompositions are added directly to irrigation water immediately prior toirrigation of the field. This technique is applicable in allgeographical areas regardless of rainfall, since it permitssupplementation of the natural rainfall at critical stages of plantgrowth. In a typical application, the concentration of theherbicide/extender composition in the irrigation water will range fromabout 10 to 150 parts per million by weight. The irrigation water can beapplied by the use of sprinkler systems, surface furrows, or flooding.Such application is most effectively done before the weeds germinate,either early in the spring prior to germination or within two days aftercultivation of the field.

The amount of the present composition which constitutes a herbicidallyeffective amount depends upon the nature of the seeds or plants to becontrolled. The rate of application of active ingredient varies fromabout 0.01 to about 50 pounds per acre, preferably about 0.1 to about 25pounds per acre with the actual amount depending on the overall cost andthe desired results. It will be readily apparent to one skilled in theart that compositions exhibiting lower herbicidal activity will requirea higher dosage than more active compounds for the same degree ofcontrol.

What is claimed is:
 1. An herbicidal composition comprising(a) anherbicidally effective amount of a thiocarbamate having the formula##STR21## in which R¹, R², and R³ are independently C₂ -C₄ alkyl withthe proviso that wherein R¹ is ethyl and R² is propyl, R³ is other thanpropyl; and (b) an amount of an organophosphorus compound sufficient toextend the soil life of said thiocarbamate, said organophosphoruscompound having the formula ##STR22## in which R⁴ is selected from thegroup consisting of C₁ -C₄ alkyl and C₁ -C₄ alkoxy,R⁵ is selected fromthe group consisting of C₁ -C₄ alkoxy and C₁ -C₄ alkylthio, R⁶ isselected from the group consisting of C₂ -C₆ alkylene and C₂ -C₆alkenylene, R⁷ is selected from the group consisting of phenyl, C₁ -C₄alkyl and C₂ -C₄ alkenyl, the latter optionally substituted with up totwo halogens, and X is oxygen or sulfur with the proviso that where R¹is ethyl, R² and R³ are both isobutyl, R⁴ and R⁵ are both methoxy, R⁶ ismethylene and X is oxygen, R⁷ is other than phenyl.
 2. An herbicidalcomposition according to claim 1 whereinR⁴ is selected from the groupconsisting of C₁ -C₂ alkyl and C₁ -C₂ alkoxy, R⁵ is selected from thegroup consisting of C₁ -C₂ alkoxy and C₁ -C₂ alkylthio, R⁶ is selectedfrom the group consisting of C₂ -C₄ alkylene, and C₂ -C₃ alkenylene, andR⁷ is selected from the group consisting of phenyl, C₁ -C₄ alkyl, and C₁-C₃ alkenylene.
 3. An herbicidal composition according to claim 1wherein said thiocarbamate is S-propyl N,N-di-n-propylthiocarbamate andsaid organophosphorus compound has the formula ##STR23##
 4. Anherbicidal composition according to claim 1 wherein said thiocarbamateis S-ethyl N,N-diisobutylthiocarbamate and said organophosphoruscompound has the formula ##STR24##
 5. An herbicidal compositionaccording to claim 1 wherein said thiocarbamate is S-ethylN,N-diisobutylthiocarbamate and said organophosphorus compound has theformula ##STR25##
 6. An herbicidal composition according to claim 1wherein said thiocarbamate is S-ethyl N,N-diisobutylthiocarbamate isS-propyl N,N-dipropylthiocarbamate and whereinR⁴ is methoxy or ethyl, R⁵is methoxy, ethoxy or methylthio, R⁶ is ethylene, methylethylene,dimethylethylene or ethenylene, and R⁷ is phenyl, isobutyl, allyl,dichloroallyl or methyl.
 7. An herbicidal composition according to claim1 further comprising a non-phytotoxic antidotally effective amount ofeither N,N-diallyl dichloroacetamide or 2,2,5-trimethyl-N-dichloroacetyloxazolidine.
 8. An herbicidal composition according to claim 7 whereinthe thiocarbamate herbicide is either S-ethyl N,N-di-isobutylthiocarbamate or S-propyl, N,N-dipropyl thiocarbamate and the antidoteis N,N-diallyl dichloroacetamide.
 9. An herbicidal composition accordingto claim 7 wherein the weight ratio of said thiocarbamate herbicide tosaid antidote is from about 3:1 to about 25:1.
 10. A method of extendingthe soil life of a thiocarbamate having the formula ##STR26## in whichR¹, R², and R³ are independently C₂ -C₄ alkyl with the proviso thatwherein R¹ is ethyl and R² is propyl, R³ is other than propyl; whichcomprises applying to the soil containing said thiocarbamate or to whichsaid thiocarbamate is to be applied an effective amount of anorganophosphorus compound having the formula ##STR27## in which R⁴ isselected from the group consisting of C₁ -C₄ alkyl and C₁ -C₄ alkoxy,R⁵is selected from the group consisting of C₁ -C₄ alkoxy and C₁ -C₄alkylthio, R⁶ is selected from the group consisting of C₂ -C₆ alkyleneand C₂ -C₆ alkenylene, R⁷ is selected from the group consisting ofphenyl, C₁ -C₄ alkyl and C₂ -C₄ alkenyl, the latter optionallysubstituted with up to two halogens, and X is oxygen or sulfur with theproviso that where R¹ is ethyl, R² and R³ are both isobutyl, R⁴ and R⁵are both methoxy, R⁶ is methylene and X is oxygen, R⁷ is other thanphenyl.
 11. A method according to claim 10 whereinR⁴ is selected fromthe group consisting of C₁ -C₂ alkyl and C₁ -C₂ alkoxy, R⁵ is selectedfrom the group consisting of C₁ -C₂ alkoxy and C₁ -C₂ alkylthio, R⁶ isselected from the group consisting of C₂ -C₄ alkylene, and C₂ -C₃alkenylene, and R⁷ is selected from the group consisting of phenyl, C₁-C₄ alkyl, and C₁ -C₃ alkenylene.
 12. The method according to claim 10wherein said thiocarbamate is S-propyl N,N-di-n-propylthiocarbamate andsaid organophosphorus compound has the formula ##STR28##
 13. A methodaccording to claim 10 wherein said thiocarbamate is S-ethylN,N-diisobutylthiocarbamate and said organophosphorus compound has theformula ##STR29##
 14. A method according to claim 10 wherein saidthiocarbamate is S-ethyl N,N-diisobutylthiocarbamate and saidorganophosphorus compound has the formula ##STR30##
 15. A methodaccording to claim 10 wherein said thiocarbamate is S-ethylN,N-diisobutylthiocarbamate or S-propyl N,N-dipropylthiocarbamate andwhereinR⁴ is methoxy or ethyl, R⁵ is methoxy, ethoxy or methylthio, R⁶is ethylene, methylethylene, dimethylethylene or ethenylene, and R⁷ isphenyl, isobutyl, allyl, dichloroallyl or methyl.
 16. A method accordingto claim 10 further comprising a non-phytotoxic antidotally effectiveamount of either N,N-diallyl dichloroacetamide or2,2,5-trimethyl-N-dichloroacetyl oxazolidine.
 17. A method according toclaim 16 wherein the thiocarbamate herbicide is either S-ethylN,N-di-isobutyl thiocarbamate or S-propyl N,N-dipropyl thiocarbamate andthe antidote is N,N-diallyl dichloroacetamide.
 18. A method according toclaim 16 wherein the weight ratio of said thiocarbamate herbicide tosaid antidote is from about 3:1 to about 25:1.